Facile Transformation of Imine Linkages and Functionalization of Aldehyde in the Covalent Organic Frameworks for Stable and Enhanced Photocatalytic Hydrogen Peroxide Production
Qinfeng Rong, Xianlan Chen, Zhiling Huang, Shuying Li, Sijing He
Abstract
Imine-based covalent organic frameworks (COFs) have been widely applied in photocatalytic hydrogen peroxide (H 2 O 2 ) production because of their highly crystalline properties and tunable chemical structures. However, the inherent polarization of C═N linkage brings a high energy barrier for π-electron delocalization, impeding the in-plane photoelectron transfer process, which leads to an inadequate efficiency of H 2 O 2 photosynthesis. In addition, the chemical stability of most imine-COFs remains insufficient due to the reversible nature of imine linkage. Herein, a quinoline-linked COF (Ald-TTB-TTA) bearing polar aldehyde groups was constructed by postsynthetic conversion of an imine COF (TTB-TTA). The expanded conjugate planes and the polar aldehyde groups facilitate the charge transfer, accelerating the proton-coupled electron transfer oxygen reduction reaction (ORR) process. As expected, Ald-TTB-TTA achieves a considerable photocatalytic H 2 O 2 production rate of 3169 μmol g –1 h –1 without a sacrificial agent, surpassing its imine-linked counterpart (1944 μmol g –1 h –1 ). Therefore, this work provides a facile strategy for designing functional COFs and is expected to aid in the construction of high-performance catalysts for the photosynthesis of H 2 O 2 .